PIC16F720-ESLASHML datasheet(92/244 Pages) MICROCHIP

92 / 244 page

PIC16F/LF720/721

DS41430A-page 92

 2010 Microchip Technology Inc.

12.1.3

SOFTWARE PROGRAMMABLE

PRESCALER

A single software programmable prescaler is available

for use with either Timer0 or the Watchdog Timer

(WDT), but not both simultaneously. The prescaler

assignment is controlled by the PSA bit of the OPTION

must be cleared to a ‘0’.

There are 8 prescaler options for the Timer0 module

ranging from 1:2 to 1:256. The prescale values are

selectable via the PS<2:0> bits of the OPTION register.

In order to have a 1:1 prescaler value for the Timer0

module, the prescaler must be assigned to the WDT

module.

The prescaler is not readable or writable. When

assigned to the Timer0 module, all instructions writing to

the TMR0 register will clear the prescaler.

12.1.4

TIMER0 INTERRUPT

Timer0 will generate an interrupt when the TMR0

interrupt flag bit of the INTCON register is set every

time the TMR0 register overflows, regardless of

whether or not the Timer0 interrupt is enabled. The

TMR0IF bit can only be cleared in software. The Timer0

interrupt enable is the TMR0IE bit of the INTCON

12.1.5

8-BIT COUNTER MODE

SYNCHRONIZATION

When in 8-Bit Counter Mode, the incrementing edge on

the T0CKI pin must be synchronized to the instruction

clock. Synchronization can be accomplished by

sampling the prescaler output on the Q2 and Q4 cycles

of the instruction clock. The high and low periods of the

external clocking source must meet the timing

requirements as shown in Section 23.0 “Electrical

Specifications”.

Note:

When the prescaler is assigned to WDT, a

CLRWDT

instruction will clear the prescaler

along with the WDT.

Note:

The Timer0 interrupt cannot wake the

processor from Sleep since the timer is

frozen during Sleep.

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